1. Field of the Invention
The invention relates to rigs comprising a structure integral with a base section designed to sit on the bottom of the sea or of a water expanse, for supporting above the water level a deck carrying scientific or industrial installations such as oil drilling installations.
2. Description of the Prior Art
The base section and/or the structure can form one or more ballastable floats, or else the deck can form a float movable along the structure. It is thus possible to build the rig on the ground, then to launch and tow it up to its laying site at which it is sunk down to the bottom by progressively ballasting the base section and/or the structure, and/or by progressively displacing the deck upwards along the structure. This laying procedure clearly does not allow the installers to lay the base section upon a precise location of the bottom of the sea or of the water expanse, as exemplified by a drilling template, and even less to fit vertically above such a location a device borne by the deck, e.g., a drilling derrick.